A battery tester that is capable of calculating its own reference values is provided. The battery tester includes test circuitry that is configured to obtain dynamic parameter values for batteries, and to compute at least one reference value based on the dynamic parameter values....http://www.google.com/patents/US7710119?utm_source=gb-gplus-sharePatent US7710119 - Battery tester that calculates its own reference values

A battery tester that is capable of calculating its own reference values is provided. The battery tester includes test circuitry that is configured to obtain dynamic parameter values for batteries, and to compute at least one reference value based on the dynamic parameter values.

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Claims(9)

1. A method comprising:

obtaining a plurality of batteries;

obtaining information related to each of the plurality of batteries;

performing at least one battery test on each of the plurality of batteries to obtain at least one test result for each of the plurality of batteries;

associating the at least one test result for each of the plurality of batteries with the corresponding obtained information related to each of the plurality of batteries;

generating a reference value based upon the test results obtained for the plurality of batteries, the reference value is for a specific battery model to which the plurality of batteries belong;

storing the reference value and a battery model code associated with the reference value in a memory;

performing a battery test on another battery, which is not one of the plurality of batteries, but of a same model as each of the plurality of batteries; and

providing a battery test output based on a comparison of measurements obtained, during the battery test on the battery that is not one of the plurality of batteries, with the reference value,

wherein the test results for the plurality of batteries comprise dynamic parameter values, and

wherein the reference value is an average of the dynamic parameter values that fall within a predetermined range of acceptable values, with the dynamic parameter values that fall outside the predetermined range of acceptable values being excluded.

2. The method of claim 1 wherein each of the plurality of batteries is on float charge when the at least one battery test is performed on each of the plurality of batteries.

3. The method of claim 1 wherein performing at least one battery test on each of the plurality of batteries to obtain at least one test result for each of the plurality of batteries comprises performing multiple tests on each of the plurality of batteries to obtain test results for each of the plurality of batteries.

4. The method of claim 3 and further comprising determining whether the test results for each of the plurality of batteries are within a predetermined range of each other.

5. The method of claim 1 wherein the plurality of batteries comprises at least 30 batteries.

6. A battery tester comprising:

battery test circuitry configured to receive information related to each of a plurality of selected batteries;

perform at least one battery test on each of the plurality of batteries to obtain at least one test result for each of the plurality of batteries;

associate the at least one test result for each of the plurality of batteries with the corresponding received information related to each of the plurality of batteries;

generate a reference value based upon the test results obtained for the plurality of batteries, the reference value is for a specific battery model to which the plurality of batteries belong;

store the reference value and a battery model code associated with the reference value in a memory;

perform a battery test on another battery, which is not one of the plurality of batteries, but of a same model as each of the plurality of batteries; and

provide a battery test output based on a comparison of measurements obtained, during the battery test on the battery that is not one of the plurality of batteries, with the reference value,

wherein the test results for the plurality of batteries comprise dynamic parameter values, and

wherein the reference value is an average of the dynamic parameter values that fall within a predetermined range of acceptable values, with the dynamic parameter values that fall outside the predetermined range of acceptable values being excluded.

The present application is based on and claims the benefit of U.S. provisional patent application Ser. No. 60/636,270, filed Dec. 14, 2004 and is a Continuation-In-Part of U.S. patent application Ser. No. 11/008,456, filed Dec. 9, 2004, the contents of which are hereby incorporated by reference in their entirety.

BACKGROUND OF THE INVENTION

The present invention relates to testing of storage batteries. More specifically, the present invention relates to a battery tester that calculates its own reference values.

Storage batteries, such as lead acid storage batteries of the type used in the automotive industry, have existed for many years. However, understanding the nature of such storage batteries, how such storage batteries operate and how to accurately test such batteries has been an ongoing endeavor and has proved quite difficult. Storage batteries consist of a plurality of individual storage cells electrically connected in series. Typically each cell has a voltage potential of about 2.1 volts. By connecting the cells in series, the voltages of the individual cells are added in a cumulative manner. For example, in a typical automotive storage battery, six storage cells are used to provide a total voltage when the battery is fully charged of 12.6 volts.

There has been a long history of attempts to accurately test the condition of storage batteries. A simple test is to measure the voltage of the battery. If the voltage is below a certain threshold, the battery is determined to be bad. However, this test is inconvenient because it requires the battery to be charged prior to performing the test. If the battery is discharged, the voltage will be low and a good battery may be incorrectly tested as bad. Furthermore, such a test does not give any indication of how much energy is stored in the battery. Another technique for testing a battery is referred as a load test. In a load test, the battery is discharged using a known load. As the battery is discharged, the voltage across the battery is monitored and used to determine the condition of the battery. This technique requires that the battery be sufficiently charged in order that it can supply current to the load.

In general, the above testers determine a condition of the battery by measuring at least one battery parameter (such as battery conductance) and comparing the measured value (for example, measured battery conductance) with a reference value (for example, rated battery conductance) for the battery parameter. The rated value(s) are typically manually entered into the battery by a tester user, for example. Relying on the tester user to determine and enter rated values can introduce errors into test results.

SUMMARY OF THE INVENTION

A battery tester that is capable of calculating its own reference values is provided. The battery tester includes test circuitry that is configured to obtain dynamic parameter values for batteries, and to compute at least one reference value based on the dynamic parameter values.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a simplified schematic diagram of a battery tester in accordance with an embodiment of the present invention.

FIG. 2 is a simplified schematic diagram showing battery test circuitry in accordance with an embodiment of the present invention.

FIG. 3 is a flowchart showing steps of a method of testing a storage battery in accordance with an embodiment of the present invention.

FIG. 4 is a simplified block diagram illustrating a battery tester memory including registers to store battery model codes and corresponding reference values in accordance with an embodiment of the present invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

FIG. 1 is a very simplified block diagram of a battery tester 100 in accordance with an illustrative embodiment of the present invention. The same reference numerals are used in the various figures to represent the same or similar elements. Battery tester 100 includes test circuitry 116 that electrically couples to a battery 112 of a battery string 111. Test circuitry 116 includes measurement circuit 121 and processor 156. Measurement circuit 121, which operates under the control of processor 156, can be any circuit configuration which is capable of carrying out different battery voltage measurements, current measurements, etc., required to determine reference values and battery test results in accordance with the present invention. In general, as used herein, reference values are average dynamic parameter values (for example, average conductance values) from a sample of “strong” batteries that are similar in condition and age.

In accordance with the present invention, battery tester 100 computes reference values and tests batteries in the string. Battery tester 100 also provides battery condition information based on comparisons between the reference value(s) and the test results. In general, computing differences between test results and reference values help in the determination of the string's capacity to provide enough conductance for the load and can also reflect how a string was treated, installed, or maintained. Although the example embodiments of the present invention described herein relate to carrying out battery conductance measurements to obtain reference values and battery test results, dynamic parameters other than battery conductance may be utilized without departing from the spirit and scope of the invention. Examples of other dynamic parameters include dynamic resistance, admittance, impedance, reactance, susceptance or their combinations.

In some embodiments, reference values are computed based on a selected percentage of batteries in the string. For example, a reference conductance value for batteries in a string can be calculated based only on measured battery conductance values that are not higher or lower than 30% from the average conductance value for the string. These limits are used because conductance values outside this range may not produce a proper reference conductance value needed for carrying out meaningful comparisons. Tester 100 is capable of testing each battery of multiple batteries in battery string 111 one at a time and comparing test results of each battery with the reference value. Tester 100 can also provide condition information for each battery based on the above comparisons. Further, the entire string is analyzed by tester 100 to determine if individual batteries are out of balance in voltage or conductance with respect to the rest of the string. Out of balance batteries are noted by test circuitry 116 and a suitable output is provided to the user via output 172. Although the above discussion regarding tester 100 primarily deals with testing battery strings, it should be noted that tester 100 can also be utilized to test individual batteries that are not a part of a string.

FIG. 2 is a more detailed block diagram of battery test circuitry 116, capable of computing the above-mentioned reference values and providing the above-mentioned test results, in accordance with an embodiment of the present invention. As in the case of FIG. 1 above, apparatus 116 is shown coupled to battery 112 (of string 111 (not shown in FIG. 2)), which includes a positive battery terminal 122 and a negative battery terminal 124.

Circuitry 116 operates in accordance with one embodiment of the present invention and determines the conductance (G) of battery 112 and the open circuit voltage (OCV) between terminals 122 and 124 of battery 112. Circuitry 116 includes current source 150, differential amplifier 152, analog-to-digital converter 154 and microprocessor 156. Amplifier 152 is capacitively coupled to battery 112 through capacitors C1 and C2. Amplifier 152 has an output connected to an input of analog-to-digital converter 154. Microprocessor 156 is connected to system clock 158, memory 160 and analog-to-digital converter 154. Microprocessor 156 is also capable of receiving inputs or information from input device 118. Microprocessor 156 also connects to output device 172.

In operation, current source 150 is controlled by microprocessor 156 and provides a current I in the direction shown by the arrow in FIG. 2. In one embodiment, this is a square wave or a pulse. Differential amplifier 152 is connected to terminals 122 and 124 of battery 112 through capacitors C1 and C2, respectively, and provides an output related to the voltage potential difference between terminals 122 and 124. In a preferred embodiment, amplifier 152 has a high input impedance. Circuitry 116 includes differential amplifier 170 having inverting and noninverting inputs connected to terminals 124 and 122, respectively. Amplifier 170 is connected to measure the OCV of battery 112 between terminals 122 and 124. The output of amplifier 170 is provided to analog-to-digital converter 154 such that the voltage across terminals 122 and 124 can be measured by microprocessor 156.

Circuitry 116 is connected to battery 112 through a four-point connection technique known as a Kelvin connection. This Kelvin connection allows current I to be injected into battery 112 through a first pair of terminals while the voltage V across the terminals 122 and 124 is measured by a second pair of connections. Because very little current flows through amplifier 152, the voltage drop across the inputs to amplifier 152 is substantially identical to the voltage drop across terminals 122 and 124 of battery 112. The output of differential amplifier 152 is converted to a digital format and is provided to microprocessor 156. Microprocessor 156 operates at a frequency determined by system clock 158 and in accordance with programming instructions stored in memory 160.

Microprocessor 156 determines the conductance of battery 112 by applying a current pulse I using current source 150. The microprocessor determines the change in battery voltage due to the current pulse I using amplifier 152 and analog-to-digital converter 154. The value of current I generated by current source 150 is known and is stored in memory 160. Microprocessor 156 calculates the conductance (G) (or reciprocally the resistance (R)) of battery 112 using the following equation:

Conductance=G=ΔIΔVEquation1
where ΔI is the change in current flowing through battery 112 due to current source 150 and ΔV is the change in battery voltage due to applied current ΔI. Microprocessor 156 also uses other information input from input device 118 provided by the tester user. This information includes the particular type of battery, the mode of operation (reference value calculation mode or battery test mode), etc.

Under the control of microprocessor 156, test circuitry 116 can test a sample (30, for example) of new or healthy batteries to obtain a conductance value representative of a new online battery (90 days after installation, for example). This reference value is stored in memory 160 and can be used to carry out comparisons with test results from a string, for example. A description of a method embodiment for testing storage batteries in accordance with the present invention is provided below in connection with FIG. 3.

FIG. 3 is a flowchart 300 showing steps of a method of testing storage batteries in accordance with an embodiment of the present invention. At step 302, dynamic parameter values for batteries are obtained. A number of sub-steps may be associated with step 302. In a specific embodiment of the present invention, the sub-steps can include:

Choosing at least 30 batteries from one manufacturer with the same make, model, power rating, age (within 6 months, for example), and service history.

Recording the following information about the batteries:

Battery manufacturer

Model number

Date of manufacture

Date of installation

Condition in which the battery operates, such as charge voltage (volts per cell), temperature, and DC current through the battery

Testing one battery, when the batteries are connected in a string, five times in a row on float charge. Here, the conductance results obtained should be within about +2% of each other.

It should be noted that if the test results do not conform to the above pattern, an electrical signal might be present in the system.

Testing each of the 30 batteries in a manner described above in connection with FIG. 2 to obtain a dynamic parameter value for each battery.
At step 304, at least one reference value is computed based on the dynamic parameter values. This can involve calculating the average conductance of all the batteries. In a specific embodiment, batteries that are higher or lower than 30% from the average conductance of all the batteries are excluded because they might be outside an acceptable (or predetermined) conductance range, and a new average conductance is calculated for the remaining batteries. The new average conductance is used as the reference value. At step 306, a selected battery is tested. At step 308, a test result obtained for the selected battery is compared with the reference value to determine a condition of the selected battery.

It should be noted that, in the above method steps, any user inputs are provided via input 118 and all computations are carried out by, or under the control of, microprocessor 156.

Of course, if a reference value for a string cannot be obtained using the above procedure, a highest conductance value for batteries in the string can also be used as a reference value. Also, a reference value can be input by a user with the help of input 118.

In some embodiments of the present invention, reference values for different models of batteries can be determined as described above and stored in memory 160 in a database. Suitable reference values from memory 160 can be utilized for carrying out comparisons based on the battery models being tested. Existing entries in the database can be modified and/or deleted and new entries can be added to the database.

FIG. 4 is a simplified block diagram illustrating a battery tester memory including registers to store battery model codes and corresponding reference values in accordance with an embodiment of the present invention. Different battery model numbers/codes can be stored in memory registers 402 and reference values corresponding to the different battery models can be stored in registers 404. Battery model numbers/codes can be received via input device 118 of tester 100 (FIG. 2). Input device 118 can comprise a keyboard input, a bar code scanner, a radio frequency receiver, etc. Microprocessor 156 is configured to suitably update registers 402 in response to receiving model information and also configured to update registers 404 when new reference values are computed. As indicated earlier, information related to model codes, reference values, battery test results, etc., can be organized in the form of a database, in memory 160, in which existing entries can be modified and/or deleted and new entries can be added. Memory locations 402 and 402 can be viewed as constituting two columns of a database 406.

It should be noted that although reference values are primarily described above as being derived from conductance values, reference values can be derived from resistance values, susceptance values, etc., without departing from the scope and spirit of the present invention.

Although the present invention has been described with reference to preferred embodiments, workers skilled in the art will recognize that changes may be made in form and detail without departing from the spirit and scope of the invention.